Compatible keyboard with the newest iPad air

Both the Magic Keyboard and the Smart Keyboard Folio are shown as compatible with the iPad Air 4th generation. See: iPad Keyboards - Apple

You can also do a search for third party keyboards "wireless keyboards for iPad" and you'll find several. Logitech makes some very good ones and so does Brydge. Neither is cheap, but then you get a keyboard which is much like a laptop keyboard - far superior to the thin, foldable kind.